This invention relates broadly to the art of flatening or leveling of metal webs or strip by passing the same between opposed groups of offset rollers. Such machines for this purpose are referred to in the art as levelers, flatteners, or straighteners and all perform essentially the same function in the same general manner.
For the purposes of background, the following U.S. patents may be referred to: Peterson U.S. Pat. No. 2,852,065; Krynytzky U.S. Pat. No. 2,963,071; Bearer U.S. Pat. No. 3,301,031; Thompson et al U.S. Pat. No. 3,638,326; Talbot 3,657,913; Ihle U.S. Pat. No. 4,107,970; and Matsui U.S. Pat. No. 4,380,921.
The basic operation theory of a leveler machine is well known. Metal is formed into strip form from a heated or cold billet or slab by passing the material between a pair of work rolls in a rolling mill to reduce the cross-section and to elongate the same. When the final thickness is achieved, and the strip exits from the mill, it is occasionally wrapped convolutely to form a coil. When it is desired to uncoil the material, a certain curvature or set remains which of course varies dependent on the radius of the portion of the strip in the coil.
It will of course be apparent that the outermost convolution will have less curvature than the innermost convolution. The leveler is designed to remove this curvature so that the strip is perfectly flat and suitable for other machining and manufacturing steps.
While the present invention could be used for removing curvature from rolled sheet material, its principal utility is for working relatively thick sheet or plate that has not been convolutely wound.
In addition to coil curvature, the sheet could have other defects such as edge waves caused by the edges being rolled thinner than its center, or "oil canning" when the reverse is true because the center was rolled thinner than the edges. In most prior art levelers, the strip is passed through a combination of rollers which provide a predetermined amount of reverse flexure sequentially diminishing as the web passes through the leveler to remove curvature and other shape defects.
In operation of the conventional leveler, as the strip passes between the rolls, a very high pressure is generated and this results in the strip tending to wedge the roll pairs apart. Accordingly, back-up rolls are provided.
Heretofore, it has been necessary for the leveler operator to carefully monitor the work roller position during the material pass, and high quality product was, to a large degree, dependent upon the skill of the individual operator.
Almost all prior art levelers include an upper and a lower series of work rollers which extend across the machine from one side frame to the other. Each series of rollers are positioned in parallel from the entry to the exit point. The upper and lower rollers are offset with respect to each other so that the web or strip passes in a tortuous path from entry to exit. In the prior art the adjustment of the vertical spacing between the upper and lower rollers is accomplished by means of wedges, jack screws or the like.
Very little development has been made to date in the field of automation of strip levelers. Two examples, however, are Buta U.S. Pat. No. 4,454,738 and Ball U.S. Pat. No. 3,596,489.